Commit 7e3f926b authored by Uladzislau Rezki (Sony)'s avatar Uladzislau Rezki (Sony) Committed by Paul E. McKenney
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rcu/kvfree: Eliminate k[v]free_rcu() single argument macro 



The kvfree_rcu() and kfree_rcu() APIs are hazardous in that if you forget
the second argument, it works, but might sleep.  This sleeping can be a
correctness bug from atomic contexts, and even in non-atomic contexts it
might introduce unacceptable latencies.  This commit therefore removes the
single-argument kvfree_rcu() and kfree_rcu() macros.  Code that would have
previously used these single-argument kvfree_rcu() and kfree_rcu() macros
should instead use kvfree_rcu_mightsleep() or kfree_rcu_mightsleep().

[ paulmck: Apply Joel Fernandes feedback. ]

Signed-off-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarJoel Fernandes (Google) <joel@joelfernandes.org>
parent ac9a7868

include/linux/rcupdate.h

+8 −21
Original line number Diff line number Diff line
@@ -957,9 +957,8 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) 


/**

 * kfree_rcu() - kfree an object after a grace period.

 * @ptr: pointer to kfree for both single- and double-argument invocations.

 * @rhf: the name of the struct rcu_head within the type of @ptr,

 *       but only for double-argument invocations.

 * @ptr: pointer to kfree for double-argument invocations.

 * @rhf: the name of the struct rcu_head within the type of @ptr.

 *

 * Many rcu callbacks functions just call kfree() on the base structure.

 * These functions are trivial, but their size adds up, and furthermore
@@ -984,26 +983,18 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) 
 * The BUILD_BUG_ON check must not involve any function calls, hence the

 * checks are done in macros here.

 */

#define kfree_rcu(ptr, rhf...) kvfree_rcu(ptr, ## rhf)

#define kfree_rcu(ptr, rhf) kvfree_rcu_arg_2(ptr, rhf)

#define kvfree_rcu(ptr, rhf) kvfree_rcu_arg_2(ptr, rhf)



/**

 * kvfree_rcu() - kvfree an object after a grace period.

 *

 * This macro consists of one or two arguments and it is

 * based on whether an object is head-less or not. If it

 * has a head then a semantic stays the same as it used

 * to be before:

 *

 *     kvfree_rcu(ptr, rhf);

 *

 * where @ptr is a pointer to kvfree(), @rhf is the name

 * of the rcu_head structure within the type of @ptr.

 * kfree_rcu_mightsleep() - kfree an object after a grace period.

 * @ptr: pointer to kfree for single-argument invocations.

 *

 * When it comes to head-less variant, only one argument

 * is passed and that is just a pointer which has to be

 * freed after a grace period. Therefore the semantic is

 *

 *     kvfree_rcu(ptr);

 *     kfree_rcu_mightsleep(ptr);

 *

 * where @ptr is the pointer to be freed by kvfree().

 *
@@ -1012,13 +1003,9 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) 
 * annotation. Otherwise, please switch and embed the

 * rcu_head structure within the type of @ptr.

 */

#define kvfree_rcu(...) KVFREE_GET_MACRO(__VA_ARGS__,		\

	kvfree_rcu_arg_2, kvfree_rcu_arg_1)(__VA_ARGS__)



#define kfree_rcu_mightsleep(ptr) kvfree_rcu_arg_1(ptr)

#define kvfree_rcu_mightsleep(ptr) kvfree_rcu_arg_1(ptr)

#define kfree_rcu_mightsleep(ptr) kvfree_rcu_mightsleep(ptr)



#define KVFREE_GET_MACRO(_1, _2, NAME, ...) NAME

#define kvfree_rcu_arg_2(ptr, rhf)					\

do {									\

	typeof (ptr) ___p = (ptr);					\